PC-Cards are connectable to computers to add functionality to the host computer. PC-cards typically contain phone modems, infrared communication devices, memory storage and devices that perform coprocessing functions. PC-cards are coupled to a host electronic device such as a computer to add the desired functionality. In addition, PC cards allow for other peripheral devices to be connected to the host computer. An advantage of the use of PC cards over other connectivity mechanisms is the ease with which PC cards may be inserted and removed, making it easy to change from one device to another. In addition, since PC cards typically contain their own microprocessors and memory storage registers, they can perform most if not all of the required processing functions internally. Therefore, by using a PC-card to add functionality to a host computer, the user does not need to load large amounts of programming into the host computer or use large amounts of data storage, saving host computer resources for other applications.
PC cards typically adhere to one or more standard. The most prevalent standard for PC-CARDS is the standard set by the Personal Computer Memory Card Association (PCMCIA) headquartered in San Jose, Calif. PCMCIA is an international standards body and trade association with over 500 member companies that was founded in 1989 to establish standards for Integrated Circuit cards and to promote interchangeability among mobile computers where ruggedness, low power consumption, and small size were critical. Today, PCMCIA promotes the interoperability of PC Cards not only in mobile computers, but in such diverse products as digital cameras, cable TV, set-top boxes, and automobiles.
Most prior art PC cards adhere to the PCMCIA 2.x standard. More recent PC cards adhere to the PC-CARD95 standard which is the successor of the PCMCIA 2.x standard. Since the PC-CARD95 standard is backward compatible to the PCMCIA 2.x, PC cards which conform to the PC-CARD95 standard use an interface connector which also conforms to the PCMCIA 2.x standard. Since the upcoming PC-CARD97 standard will be backward compatible with the PC-CARD95, as is anticipated with all future releases of PC-CARDxx standards, cards which conform to future anticipated standards may use an interface connector that conforms to current standards. A device which follows the electrical, physical and logical PC-CARD standard guidelines will be referred to in this application as "PCMCIA" or "PCMCIA-compliant".
However, for complex applications it is desired to provide a device which can connect and operate through different interfaces. To connect to a non PCMCIA-compliant interface, a different PC-card is typically used which has the required non-PCMCIA-compliant interface. In order to connect to any different non-PCMCIA-compliant interface, a different PC card which includes the different non-PCMCIA-compliant interface is required. Thus, in order to provide a function through multiple interfaces, several PC-cards are required which may include the same or similar internal processing devices and algorithms, but which interface differently with different interfaces. For example, to incorporate connection to a PCMCIA-compliant interface, and two different non-PCMCIA-compliant interfaces, three PC-cards would be required, each having a different interface. In addition, each PC-card has less versatility than desired because of the lack of connectivity to other interfaces.
One possible solution to this problem is the use of additional connectors on each PC-card. However, due to the form factor constraints imposed on PC cards, and in particular PC-cards adhering to the PCMCIA standard, the incorporation of additional connectors into the PC-card itself is not feasible. This is primarily due to the fact that multiple connector designs are difficult, if not impossible, to integrate into the small housings of the PC-card. Thus, multiple connectors are seldom incorporated into the PC-card housing.
Another possible solution is the use of multiple connectors which are coupled by cable to the PC-card. However, the resulting device is bulky, expensive to manufacture and difficult to operate. Because of the multiple cables and connectors, the device is confusing and difficult to operate. In addition, the device is not as reliable and as easy to maintain as devices which do not contain multiple cables and connectors.
Though additional connectors could be added to the device to allow for connectivity to multiple interfaces, it would be difficult to determine which interface is to be active at any particular time. This is particularly critical in the situation when multiple functionality is combined with the multiple interface problem. For example, when the function to be performed by the device is dependent on the interface to which it is attached, it is difficult to determine which function to activate within the device. One possible solution would be to incorporate hand operated switches. However, due to form factor constraints, hand operated switches are impractical and difficult if not impossible to integrate into the device without violating the PCMCIA and PC CARD 95 standards. In addition switches are expensive and they present reliability and maintainability problems. Also, switches make the operation of the device more complex and hence more difficult for the user.
The complexity of electronic devices such as PC-cards has been steadily increasing. Therefore, more features and functions are required to be incorporated into each device. However, the incorporation of increased functionality into PC-cards is often infeasible due to the restrictions imposed by the PCMCIA standard. Due to the problems associated with the incorporation and use of switches on PC-cards, switches typically are not placed on PC-cards.
Typically, multiple functions are obtained by using multiple PC-cards. For example, a first PC card which provides a first function is inserted into the host computer to access a specific set of functions. When a second set of functions is needed, the first PC card is removed and a second PC card is placed into the PC card receptacle on the host computer. Thus, even if the connectivity problems could be overcome, the PC-card has no way to distinguish between connections that may dictate different sets of functions. For example, it may be desirable to perform different functions when the PC-card is inserted into a charger and/or an adapter than would be performed when the PC-card is installed into a PCMCIA compliant interface. In addition, it may be desirable to perform a entirely different set of functions when the PC-card is not inserted into any host. Prior art systems typically have no way to distinguish between these different interfaces and no way to distinguish the lack of connectivity to an interface.
What is needed is a way to overcome the connectivity limitations of PCMCIA and PC-CARD 95 compatible devices. More specifically, what is needed is a PC Card which has an interface compliant with PCMCIA standards which will also allow for connectivity of different electrical interfaces. In addition, what is needed is a method of using a PCMCIA standard interface which will allow multiple different electrical interfaces to work over a single PC card connector alternately. In addition, there is a need to detect the type of interface that is being used so that different sets of functions may be performed by the device which are dependent on the interface being used. The present invention provides a single elegant solution which satisfies all of these needs.